Retailers Using USPS for Last-Mile Delivery Seek New Sorting Options

It’s no secret that major changes are occurring in parcel delivery, with parcel carriers increasingly teaming up with the United States Postal Service (USPS). The parcel carries utilize their transportation networks to deliver packages close to its final destinations — often to a local post office — and the USPS takes it from there to recipients’ homes or businesses.

This approach, typically called last-mile service, is generally less expensive than normal United Parcel Service (UPS) and FedEx ground services because USPS carriers are already visiting each residence and business every day so they can deliver the packages along with their regular mail deliveries at a lower cost. The last-mile delivery services unify the USPS, UPS and FedEx delivery tracking systems so customers only have to manage one tracking number.

The challenge for omnichannel retailers and other potential customers of this service is that using this new technology requires the ability to economically and quickly sort a wide range of different types and sizes of packages to the ZIP code level. Conventional sorting systems are too large and expensive to cost effectively meet these requirements.

For example, the facility for one major company occupies over 4 million square feet and contains more than 17,000 feet of conveyor. This isn't an effective solution for the delivery of low-weight articles. At the other end of the spectrum, many companies currently processing low-weight parcels and flats are manually sorting, which isn't cost effective in this application.

Consequently, omnichannel retailers and others that wish to use the USPS for last-mile delivery of low-weight articles need a low-weight parcel and flats sorting system tailored and priced to meet their needs.

A critical aspect of a parcel sorting system is the reading of the barcode on a package or flat as it travels down the line at high speeds. The wide variation in the shapes and sizes of these items present a challenge that requires a vision system able to maintain high read rates at constantly changing focal lengths. In addition, many items are shipped in flexible plastic or poly-wrap envelopes that take on the shape of the contents. This distorts the barcode on the envelope, making it hard for a vision system to read.

Today’s sorting systems normally use line-scan vision cameras. A line-scan camera has a single row of pixel sensors that capture image frames as the article moves past the camera. These image frames are continuously fed to software that joins them to each other to make a complete image.

With image-based technology, there are really four steps to reading a barcode: take an image of the article, find the barcode in the image, generate a signal and decode it. Technology can improve the signal generation and decode phase by improving signal quality and increasing the speed of signal acquisition.

Shane LaChappelle is a sales engineer and ID specialist at Cognex, a company that designs, develops, manufactures and markets a range of products that incorporate machine vision technology.